This invention relates to a method of joining piping materials, which is suitable for joining two thin-walled stainless steel pipes and for joining a metallic pipe and a metallic pipe coupling.
It is well known to join piping materials such as metallic pipes, pipe couplings, etc. with a technique to thread end portions of the piping materials and screw one piping material into the other. However, such method has not been satisfactory with respect to workability, pressure resistance, airtightness, etc. The present applicant has previously invented a joining method to form a diametrically enlarged portion at an end portion of one piping material, i.e. a tapered portion, to which an annular gasket having a wedge-shaped cross-section is interposed and further an end portion of the other piping material is inserted, followed by application of pressure from the periphery to achieve plastic deformation of the diametrally enlarged portion. This is disclosed in Japanese Provisional Patent Publication No. 130729/1982. Also, according to subsequent studies by the present applicant, it has been found that more effective joining can be done by inserting a C ring as shown in Japanese Unexamined Utility Model Publication No. 75582/1986 together with the annular gasket into the diametrally enlarged portion.
In the method as mentioned above, for plastic deformation of the diametrally enlarged portion, joining the piping materials to each other was effected by approaching in the axis direction a first jaw having a lateral cross-sectional shape with the tapered planes of clamping action and a second jaw having a tapered planes of clamping action in the opposite direction thereto. Therefore, the jaws of the joining tool are required to move complicatedly, thus causing the size of the joining tool to be too large. This is particularly problematic because it is impossible to effect joining of piping materials near walls.